Grease recommendations for worm gear?

[John Garza (3665)]

I started out using Radio Shack multi-purpose lube gel back in the 90's. Works well but eventually dries/dissipates after 15 years or so and must be re-applied.

I really didn't think much about the grease until...
I recently bought a 67 with a refurbished card reader. I noticed the card reader was a little quieter than the repair jobs I do. That impressed me. What didn't impress me was the number of misreads. Then I noticed a pattern - after 5 or 6 passes of the card through the reader it was suddenly reliable on every read. I suspect they used a thicker grease that made it quieter but needed a little 'warm-up' through the gears to reduce viscosity. Any ME's out there care to consider this?

[teenix]

15 years isn't so bad, I might be gone by the time it fails again :-)

Did HP put lube on these in the first place, given that it may fling off into the calculator internals?

They might be the same as the printer gears in Topcats which have none.

There should be a tiny dob of molybdenum grease on the end float bearing though which helps keep things quiet.

cheers

Tony

[Hans Brueggemann]

(02-07-2023 03:39 PM)John Garza (3665) Wrote:  I started out using Radio Shack multi-purpose lube gel back in the 90's. Works well but eventually dries/dissipates after 15 years or so and must be re-applied.

I really didn't think much about the grease until...
I recently bought a 67 with a refurbished card reader. I noticed the card reader was a little quieter than the repair jobs I do. That impressed me. What didn't impress me was the number of misreads. Then I noticed a pattern - after 5 or 6 passes of the card through the reader it was suddenly reliable on every read. I suspect they used a thicker grease that made it quieter but needed a little 'warm-up' through the gears to reduce viscosity. Any ME's out there care to consider this?

no, this is not about warming up, it's the worm gear breaking free by "combing out" clogged debris and dust. also, the motor shaft requires some tiny amount of "play" (approx. 0.5 mm) in the lateral direction after the gear has been re-installed.
another reason for a louder than expected reader is a too tight adjustment of the excenter pin. you can try and test it by giving it a quarter turn in either direction and redo a test run with a card.
when repairing the cardreader, it is a good idea to thoroughly clean the gear from old grease residues before applying new grease. stay away from mineral greases, as they might deteriorate the main gear wheel (never experienced that on my repairs. however, better safe than sorry).
i'm using ÄRONIX 6900 PTFE paste for all repairs, which is known for not deteriorating materials like nylon or delrin (among others). not sure as to whether that is available outside of germany, though.

[Jeff_Birt]

I tend to use white lithium grease unless the manufacturer specifies something more exotic. There are a lot of myths out there that lithium grease is bad for plastics, they are just that, a myth. Most DIY type websites I have found have wildly inaccurate information about this subject. It is best to go to a manufacture's website for factual information.

You can get into a lot of trouble with various combinations of rubbers and greases. Different plastics and rubbers will react differently to different solvents as well. For example, most types of rubber can be cleaned with alcohol, a few types will be permanently damaged by alcohol. I have mostly come across these types of rubber things like paper feed rollers, printer/typewrite platens, etc. For those applications I stick with soap and water.

https://3dinsider.com/plastic-gear-lubricants/

https://www.lubriplate.com/Products/Grea...S-ES/DS-ES

[John Garza (3665)]

All the classics and topcats I've repaired had some dark oily residue on the worm gear, so I presume it was lubed. 41Cs have a yellow grease. Yes, I lube the tip of the axle that goes in the hole as well as the worm gear threads themselves - and of course after cleaning out the threads with a toothbrush. And I do check for play and free movement before reassembly. Perhaps I wasn't clear - it always misreads the first few times - then works reliably. And this after a refurb so there is zero debris and dirt in the gears. If you don't lube the worm gear, you will be surprised at the amount of gear noise generated. It is much quieter if you lube it.

[Hiwi]

Bigger noise may depend on the condition of the slip clutch and position in the worm gear.

The engine shaft should reach up into the drilling (inner hole) of the gear.

If it is not deep enough the gear doesn't run smoothly and of course louder.

I use one drop of Ballisitol or Slicongearlube which i use since years for the gears of my modelhelicopter.

Ralf

[David Hayden]

I used finish line dry bike lubricant on a Nikon film scanner years ago and it's still going like a champ. The lube is a teflon powder. I don't know how it would work in a card reader. The obvious concern is the possibility of powder coming off and getting on the read/write head.

[GanjaTron]

Hi all,

thought I'd join in this discussion as I'm having issues with a HP65 card reader. It worked fine for some 10 years after I replaced the gummy wheel with silicone tubing, but suddenly locked up a few weeks ago. Having inspected it, I now realise the motor is actually loose, with the worm gear no longer centered and wobbling against the frame.

If I align the motor without fully tightening the two screws that attach it to the frame, it runs fine and draws the requisite 180-200 mA unloaded. But if I tighten the screws, the motor experiences severe resistance and draws in excess of 400 mA! I get the impression the worm gear is either too long or its bearing is worn.

Should I apply lube to the worm gear bearing, or should I be looking at the clutch? The motor doesn't slip, so I didn't feel the need to mess with the latter yet. (Nor do I really want to!)

I can also confirm there's some black residue on the worm gear, and the motor is indeed loud and emits a horrible screech sometimes. So I may apply some lube on the worm gear following the advice here, in the hope it doesn't transmit to the card and the head. (I've got some silicone paste somewhere).

Thanks for any suggestions,

--Roland

[Danito-Danone]

Hi John, I applied special silicone grease for metals years ago and the card reader works very well. D-D

[John Garza (3665)]

Roland,

I had the same screeching issue with a 65. First thing to ensure is the wheel turns freely - a small flatblade screwdriver pushing the gear-teeth along should feel close to no resistance to the hand. Then ensure the worm gear and tip are lubed. If all that is done and it still screeches it's time to look at the connection between the worm gear and motor (aka clutch). I've had good luck with tubing and even RTV silicone pushed into the sleeve and then embed the worm gear within it. After it dries, it can still be pulled out by hand, but it provides good grip. -J

[John Garza (3665)]

About lube getting on the mag head and cards. As a reminder, we are talking about grease, not oil. In particular the paste or gel type. And only a little, applied with a toothpick. I've been doing this for nearly 30 years and never got a contaminated card. In fact, one reason I originally chose the RS multi-purpose lube was that the package said 'stays where you put it', as I initially feared the worst case scenario - grease splattered all over the inside of the machine. But the centrifugal force is insufficient to overcome the adhesion to the gear-teeth. So it stays put.

[teenix]

(02-08-2023 02:52 PM)John Garza (3665) Wrote:  Perhaps I wasn't clear - it always misreads the first few times - then works reliably.

I wonder if replacing the 47uF and/or the 22uF tantalum capacitors in the power supply would help.

cheers

Tony

[GanjaTron]

Hi John,

thanks for the info. Actually, I think the screech comes from the worm gear gnashing into the gear. ;^)
Btw, any idea what's in RS's multipurpose gel?

I think I intentionally didn't fully tighten the screws when I first refurbed the card reader as I ran into exactly the same issue; motor jams when fully tightened.

Just to clarify: by pushing the gear wheel by hand, do you mean with the worm gear installed or without? There is no way you can push the wheel in the former case, and I assume this is by design.

Dumb question: has anyone here lubed the motor itself, and is this advisable/necessary? I assume its bearing must be dry after all these decades, but not sure how to even access them.

I've refurbed the card readers in my two HP-97's and opted not to lube them. So far so good, but one now also screeches, so might have to go this route next time round.

--Roland

[GanjaTron]

(02-08-2023 09:44 PM)teenix Wrote:  I wonder if replacing the 47uF and/or the 22uF tantalum capacitors in the power supply would help.

Do tantalums exhibit the same gradual recovery behaviour as electrolytics? My (albeit limited) experience is that they tend to short spontaneously -- when they don't decide to explode, that is. ;^)

Btw, one of the caps in my HP65's PSU reads 11 ohms ESR! While that doesn't sound right, I doubt it's the cause of the card reader woes. I checked the motor with my bench supply, and it's definitely a mechanical issue.

--Roland

[John Garza (3665)]

Roland, I'd say definitely lube the worm gear. As I wrote earlier, it's mechanical blockage keeping the wheel from spinning unimpeded, lack of lubrication, or the clutch. If you have no lube, that's the most likely problem. And I've never lubed the motor internals, you don't need to do that. I was lucky to notice the same Swiss made motors (with worm gears!) sold by Edmund Scientific many years ago - so I picked up a box of them JIC. But I never needed to replace a motor.

Tony, I didn't think about the tantalums. That's a good idea. I've replaced them on others, but they always failed consistently - not intermittently and in a pattern. But I can say after a 100 cards or so, it's getting more reliable. I will only occasionally get a misread on the first pass, and zero on the second. Maybe the grease is getting 'smoothed out', maybe the caps are getting reformed, not sure at this point.

On tantalums, I've never seen any explode on calcs. But they do on power supply lines for the vintage S100 systems I have. Much more current flows through them than on a calculator. Powering up unused equipment with a variac will reduce such surprises. As a rule, on the S100 systems I keep operational, I recap all the cards. Ceramics I keep, but tantalums and electrolytics are replaced without testing - I assume they are bad or will be shortly. Cheap insurance!

[John Garza (3665)]

I should also mention it is more aesthetically pleasing to have a whisper quiet card reader than a noisy one. To me, it somehow exudes a sense of quality. Which I think is appropriate for these HPs. On the ones I have now, the motor/gear noise is on par with the faintly audible 'ting' you hear (from the gold contacts releasing the card) when you pull the card out the exit slot. That's quiet.

[teenix]

(02-08-2023 09:56 PM)GanjaTron Wrote:  

(02-08-2023 09:44 PM)teenix Wrote:  I wonder if replacing the 47uF and/or the 22uF tantalum capacitors in the power supply would help.

Do tantalums exhibit the same gradual recovery behaviour as electrolytics? My (albeit limited) experience is that they tend to short spontaneously -- when they don't decide to explode, that is. ;^)

Btw, one of the caps in my HP65's PSU reads 11 ohms ESR! While that doesn't sound right, I doubt it's the cause of the card reader woes. I checked the motor with my bench supply, and it's definitely a mechanical issue.

--Roland

There has been issues with the degraded PSU caps and card read errors, so I thought it may be worthwhile replacing them. Maybe the motor tantalum cap as well. Has the calculator been on for a while, or just turned on when the problem occurs?

cheers

Tony

[GanjaTron]

(02-09-2023 11:02 PM)teenix Wrote:  There has been issues with the degraded PSU caps and card read errors, so I thought it may be worthwhile replacing them. Maybe the motor tantalum cap as well. Has the calculator been on for a while, or just turned on when the problem occurs?

The card reader issue first appeared when the calc had already been powered up for 15 minutes or so and successfully ran the card through several times. There was absolutely no change after that. Of course I'm not ruling out a compound issue with the tantalums as well, but there's clearly a mechanical problem with the motor and worm gear.

--Roland

[albertofenini]

I would strongly advise to follow Tony advice

On our HP67s and HP65s changing the Caps has done miracles, it has solved problems like

"motor keeps running when the card has gone thru"
"reads and writes once in a while"
"reads only one card out of all"
"writes but doesn't read back"

and we could list a few more, that apparently could have been due to mechanical issues
we usually don't lube the worm gear though this is a very good idea

Just my two cents ... take care !!

(02-09-2023 11:02 PM)teenix Wrote:  

(02-08-2023 09:56 PM)GanjaTron Wrote:  Do tantalums exhibit the same gradual recovery behaviour as electrolytics? My (albeit limited) experience is that they tend to short spontaneously -- when they don't decide to explode, that is. ;^)

Btw, one of the caps in my HP65's PSU reads 11 ohms ESR! While that doesn't sound right, I doubt it's the cause of the card reader woes. I checked the motor with my bench supply, and it's definitely a mechanical issue.

--Roland

There has been issues with the degraded PSU caps and card read errors, so I thought it may be worthwhile replacing them. Maybe the motor tantalum cap as well. Has the calculator been on for a while, or just turned on when the problem occurs?

cheers

Tony

[John Garza (3665)]

As per spec... the HP-97 service manual recommends lubricating the thrust bearing (the tip of the worm gear) with molybdenum disulphide grease. Dow Moly G or equivalent.

Basic Moly disulphide grease is black - matching the residue on worm gears from classic machines.
Dow Moly G-1056 is yellow in color - similar to the residue on 41C worm gears.

Other than Dow, Yamaha sells this type of grease on Amazon.

-J